Light emitting diodes (LEDs) are semiconductor light emitting devices emitting light when a current flows therethrough, and converting electrical energy into light energy through PN junction diodes configured of gallium arsenide (GaAs) or gallium nitride (GaN) light semiconductors. Regions of light emitted from the LEDs include blue, green and white in a range of red (630 nm to 700 nm) to blue-violet (400 nm). Such LEDs have positive attributes such as relatively low power consumption, high efficiency and long lifespans, as compared to light sources according to the related art, such as incandescent lamps, fluorescent lamps, or the like. Thus, demand for LEDs has continuously increased.
In recent years, LEDs have come into widespread use, and the range of uses thereof has been increasingly expanded to encompass miniaturized lighting devices for mobile terminals, vehicle lighting devices, indoor lighting devices, lighting devices for outdoor signs, and the like. In particular, the application of LEDs has been increasingly expanded to include lighting devices for signs.
FIG. 1 is a cross-sectional view of a double-sided illuminated sign using a general LED.
In the case of a general LED 11, unlike a fluorescent lamp, light from individual LEDs is only irradiated onto a single light emission surface, and is not irradiated to a surface thereof opposite thereto. Thus, it is necessary to dispose the LED 11 and a diffusion plate 13 on both sides of a circuit board 12, as shown in FIG. 1. Thus, a problem in which the configuration of a double-sided illuminated sign using an LED is relatively complicated and an amount of LEDs is increased may occur.